Summaries of the Issue
The paper reviews control algorithms of electromechanical systems using the theory of fuzzy logic, describes basic principles of synthesis of these systems, discusses methods for analyzing their stability based on fuzzy Lyapunov functions. These algorithms are most often implemented in the form of various controllers, which application is justified in the systems with unknown mathematical model, or not determined, or strictly nonlinear, with nonlinear disturbances in their structure or in the external forces. We describe the basic methods of inference used in the design of various types of fuzzy logic controllers proposed by Zadeh, Mamdani, Takagi, Sugeno, and Mendel. A typical structural scheme of such controllers is given. The considered applications of these controllers in the control of various technical plants give the possibility to classify them according to various criteria: topologies of structures, inference mechanism, methods of defuzzification, types of membership functions. We review methods for adjustment of such controllers by genetic algorithms and neural networks with a description of the most commonly used criteria for optimality estimation. It is shown that the use of an expert approach based on fuzzy logic is applicable both in control of various coordinates of information subsystems of robotic complexes, and in control of the power switches of their energy subsystems. In the review of publications, the main attention was given to sources containing comparison with traditional approaches to control, as well as sources in which theoretical studies are supported by experiments involving various electromechanical plants. The paper may be useful to specialists and researchers in the field of control of various technical devices.
Subject of research. The paper presents the study of effect that external cavity length with the fiber Bragg grating has on the spectrum of Vertical Cavity Surface Emitting Laser (VCSEL) with a central emission wavelength of 1554 nm. Fiber Bragg grating reflection coefficient was 95 % and full width at half maximum (FWHM) was 0.095 nm. Method. An interrogator was used for emission central wavelength measurement over time. We performed the study of the standard deviation and drift of the VCSEL central wavelength, both with and without an external cavity. The studied external cavity length varied from 1040 to 30 mm by decreasing the fiber length. Main results. As a result of the study, the dependence of the VCSEL spectral characteristics on the external cavity length was obtained. It was also shown that the VCSEL center wavelength variation was reduced by more than an order of magnitude, so 3σ standard deviation was 0.17 pm using an external cavity 1040 mm long, in contrast to 8 pm for the case without an external cavity. We showed the possibility of reducing the amplitude of the central wavelength drift to one-fourth, from 2 to 0.5 pm, with the use of an external cavity. Practical relevance. The study proves to be useful when creating fiber-optic distributed sensors of physical quantities with affordable cost, if the design requires the use of a highly coherent emission source.
Subject of study. The paper presents the study of temperature value effect on the h-parameter in birefringence optical fibers for different samples: fibers with an elliptical tension cladding with a double acrylate coating (250 μm in diameter), Bow-Tie fibers with a double acrylate coating (170 μm in diameter). Method. The research method is based on wideband interferometry application. We used polarization scanning Michelson interferometer with the central wavelength of the optical source equal to 1575 nm and the width equal to 45 nm. The temperature was changed by thermostat up to +70 °С, and by “dry” ice down to –70 °С. Main results. It was found that the value of the h-parameter increases from ~10-7 1/m at +22 °С to ~10-3–10-4 1/m at –70 °С in the negative temperature region, while in the positive temperature region h-parameter variation is insignificant for all fiber samples. Practical relevance. The scanning Michelson interferometer can find wide application in birefringent optical fiber production for its quality analysis: the absence of local defects, control of the fiber h-parameter value and beat length. Understanding of the temperature effect on the h-parameter value in birefringent fibers used in creation of fiber-optic sensors, will expand the performance characteristics of the developed device, as well as improve its accuracy parameters.
Subject of research. This paper presents developed techniques for research of the spatial structure changes of protein molecules when the state of these molecules is close enough to that one in living organisms, actively participating, as enzymes, in regulating the metabolism of the latter. Method. The synchronous photofluorescence spectra of aqueous solutions of casein milk protein were studied in the visible and near ultraviolet regions at different shifts of emission wavelengths relative to excitation wavelength (Dwl). Main results. Significant differences were observed both in the intensity and in the position of light scattering peaks and the own molecular photofluorescence of casein water solutions not only at different concentrations of the protein component in them, but also depending on the duration of casein presence in a dissolved state. Apparently, this fact was due to the differences in the spatial structure of protein molecules in the studied solutions (determined, in turn, by different degrees of hydrogen and Van der Waals interactions of these high-molecular compounds together with the water molecules surrounding them). Practical relevance. It was demonstrated that photoluminescence techniques provide the researcher with a fairly simple, reliable and informative way of studying both thermodynamic and kinetic aspects of the interaction of protein molecules, which are in a state close to the native, with the surrounding molecules of the other substances (including water). The synchronous spectra of the intrinsic molecular photofluorescence of aqueous protein solutions can be used for this, which are recorded at Dwl = 10 nm in the excitation wavelength range from 230 to 600 nm. Whereas similar spectra recorded at Dwl = 0 and 90 nm can be recommended for more sensitive quantitative determination of the protein content in aqueous solutions.
Subject of research. We study conditions of fractal crystals growth on the high-temperature material surface under pulsed laser radiation impact. Method. Comprehensive studies were performed on the metal surface morphology after impact of microsecond laser pulses by optical and electron microscopy for analysis of the size of the melting zone and the presence/absence of surface fractal crystals. The experimental data were used to calculate the possible thickness of the melt layer for specific parameters of laser radiation. According to the calculated data, the range of calculated values of the melting layer thickness was determined, at which the stable growth of fractal crystals on the surface of stainless steel occurred. The parametric variation of the laser pulses was carried out in the following ranges: energy in the range of 10–15 J, pulse duration in the range of 6–12 μs, spot diameter in the range of 0.4–2 mm. Main results. Combinations of parameters for formation and stable growth of fractal clusters as the dendrites form were determined. The reliability of the estimates obtained were tested on another type of stainless steel with drastically different characteristics. Practical relevance. Research results are applicable for parameters determination of pulsed laser radiation exposure to obtain surface morphology with desired properties.
Subject of research. During the winter phenological period, the largest part of the solar radiation flux is reflected from the earth's surface. The reason is the presence of snow cover on the earth's surface, which has high reflectance of the radiation flux. Under these conditions, the choice of shooting modes of the Earth from space is limited. Long exposure modes cannot be selected. As a result, the pictures have low quality and their interpretation is difficult. The proposed method provides the images of the earth's surface suitable for processing in view of the space survey features in winter phenological period. The method significance is confirmed by the results of the contrast evaluation of satellite images. Method. The method is based on the idea of co-processing of a series of space images with different exposures. The result of processing is a snapshot with an extended dynamic brightness range possessing high contrast in the areas of dark and pale halftones. Such snapshot displays better the borders and details of geographic area objects and that simplifies significantly its interpretation. Main results. We analyzed the effect of space survey ballistic conditions on the results of method application for image quality improvement in winter phenological period. The conclusion was drawn that the results of joint processing of images with different exposures can be ill-posed. The cause lies in geometric distortions due to continuous relative motion of the observed area and a spacecraft. The variant to eliminate geometric distortions by camera engineering development is proposed. Practical relevance. The prossessing method for the Earth's remote sensing data provides obtaining suitable for interpretation satellite images of the objects located on the earth surface in any phenological period. The results are applicable for the information accuracy increase in survey and cartography support.
Subject of research. The paper considers the approach to generation of pulse optical jamming signals in broad range of wavelengths aimed to suppress visual optical and electro-optical channels of surveillance equipment operating in different spectral bands. Method. The high-intensity emission optical source was created utilizing compact cermet case short-arc high-pressure xenon lamps with internal reflectors. Optical emitter with multiplication of lamps was used in order to attain the values of energy density above the specified criterion levels at the distances of suppression. Main results. The emitter was constructed for visual-optical jamming in the spectral range of 0.35-2.5 μm with maximum light intensity of 95∙105 cd and irradiance of 120 W/m2 at 10 meters. The low-frequency modulation varies from 5 to 15 Hz while the high-frequency modulation of low-frequency pulses is kept constant at 5 kHz with 60 % modulation depth. The beam width can be mechanically switched from 6 to 15°. The emitter is embodied in all-climate type of enclosure and can be operated from –40 to +50 °C and air humidity up to 98 %. Practical relevance. Implementation of cermet case short-arc high-pressure xenon lamps with fixed integrated reflector provides an opportunity to construct compact high-power emitters of pulsed optical signals. The lamps are explosion-proof and not prone to devitrification and depressurization. The emitters utilizing the lamps with internal reflectors do not require in-service adjustment, have high reliability and durability. The emitter can be configured with the lamps of variant optical power in order to satisfy the electrical power availability of delivery vehicle of all kinds.
AUTOMATIC CONTROL AND ROBOTICS
The paper deals with the problem of identification of linearly varying frequency of sinusoidal signal with unknown amplitude and phase. Identification task for linearly varying frequency occurs, for example, during telescope operation control and it is of practical interest. Existing synthesis methods for identification algorithms of linearly varying frequency of sinusoidal signal use unlimited functions of time that is not attractive from a technical point of view, since the measurement noise multiplied by an unlimited function tends to give extremely poor estimates of the tunable parameter. This paper proposes a new approach for identification of linearly varying frequency comprising iterative filtering of measured sinusoidal signal (with the use of linear first order stable components), which in turn gives the possibility to obtain a simple linear regression model with one unknown constant parameter. We present computer simulation results, illustrating the performance of the proposed identification algorithm. Computer modeling was performed both in the presence and absence of the measurement noise. Also, comparative analysis of the proposed approach with the previously obtained methods was carried out within the framework of computer simulation. It was shown that the presented solution provides a significant improvement in the accuracy of an unknown frequency identification in the noise presence.
Subject of research. We consider dynamical system optimal control problem relating to a class of conditional variation problems with variable endpoints. Variational method is applied for research of the elastic mechanical system with controllable spring stiffness. Methods. The classical calculus of variational methods is used, which includes a variation of auxiliary functional and corresponding Euler equations. In solving a general conditional variation problem, the obtained differential system of equations in closed form is studied for design of an optimal control system for the initial dynamic object with a given quality functional. Main results. Results of unconstrained optimization are generalized to the case with additional differential (nonholonomic) constraints. Transversality condition in the variational problem is formulated in terms of local programming. An optimal control algorithm is constructed in the elastic oscillator model example, and the value of finite transition period is found. Practical relevance. The proposed approach can be used in optimal control design for dynamical systems. This optimization scheme can be also applied to controlled dynamic systems, when operation time is not fixed in advance.
MATERIAL SCIENCE AND NANOTECHNOLOGIES
Subject of research.The features of diazo dye Chicago Sky Blue 6B photodecomposition in aqueous solutions containing the salts of zinc, aluminum and erbium were studied. The paper presents the research of effect of the type and concentration of salts of these metals on the spectral properties of solutions and kinetic dependencies of the decomposition processes of a diazo dye under the action of UV radiation from DRT-240 high-pressure mercury lamp. Method. The methodology of the studies consisted in the sequential measurement of the absorption spectra of the solutions on a Perkin-Elmer Labda 650 spectrophotometer in the UV and visible parts of the spectrum after UV irradiation of various durations and analysis of the observed spectral changes. Main results. Based on the research carried out, it was shown that the absorption spectrum of the dye changes in the presence of metal salts in solutions and an additional maximum appears on the characteristic broad and intense absorption band of the dye in the visible part of the spectrum (λ = 540–680 nm). That fact suggests the behavior of dye molecular structuring. When metal salts are introduced into the solution, the mechanism of its decomposition under the action of UV radiation also changes significantly. In the presence of metal salts, along with a decrease in the intensity of the absorption band of the dye in the visible part of the spectrum, its substantial shift to the shortwave region is also observed. Studies of the dye decomposition kinetics under UV irradiation showed that the rate of the dye photodegradation sharply increases in the presence of metal nitrates in solutions. The introduction of zinc nitrate into the solution has particularly strong effect on the dye photodegradation in an aqueous solution. Practical relivance.The experimental results obtained can be used in the development of photochemical processes for the purification of water from organic pollutants.
A new, integrated, instrumental, optical-electrochemical, microbiotesting system is described. This system can be used to assess the toxicity of various products and wastes, as well as the degree of environmental safety of various rooms, reservoirs, territories and sources of environmental pollution. A technique is presented as an example of the analysis carried out using the described system. This technique comprises incubation of Chlorella vulgaris tanks for 12 hours in the presence of various concentrations of 5 typical oil products in an aqueous solution containing sucrose with various mineral additives. At the same time, the elastic light scattering efficiency in the wavelength range of 820–915 nm (Iod), the optical density in the wavelength range of 435±5 nm (Avd) and the value of the redox potential (Е) were measured in each of the mentioned containers during the entire time of their incubation with an interval of 60 minutes. Then, ΔIod/Δτ, ΔAvd/Δτ, ΔE/Δτ values were calculated at each time τi, as well as partial and total degrees of activation or inhibition (+/–) of C.vulgaris vital activity by given concentration of each tested oil products. As a result, it was shown that the change in Iod characterized to a greater extent the intensity of growth and reproduction of C.vulgaris; whereas the change in E characterized to a greater extent the metabolic activity of test microorganisms. At the concentrations of the tested oil products equal to 2×10–3 vol.% and more, the higher concentrations of these products were in the medium and the more they contained aromatic components and chemically active groups, the greater degree of inhibitory effect on C.vulgaris they had. On the other hand, at the concentrations of the same oil products equal to 2×10–5 vol.% and less, the vital activity of C.vulgaris was activated even by very chemically active aromatic hydrocarbons. Moreover, the degree of such activation was so much the less, the more heterogeneous mixture of various hydrocarbons was present in the test sample. Thus, we were certain that the presented microbiotesting system provides the researcher with a sensitive, express, accessible and informative method for assessing the pro- and antimicrobial activity of various products and wastes, as well as the environmental safety of various premises and territories.
Subject of study. We propose detection method for potential defects in the structure of device made of materials with high thermal conductivity, and thermal conductivity determination by the method of contact-free noninvasive thermal-imaging macrography. Method. The principle of the method lies in the following: local heating and cooling of the device is carried out, the temperature fields of its surfaces are measured. This method is based on the analysis of temperature fields. Main results. The study on the presence of defects in highly heat conductive material based on silicon carbide with diamond filling was performed. The experimental setup was developed. It consists of a measuring cell, a test sample with a cooler installed on the one edge and electric heater on the opposite edge. The test samples had the form of silicon carbide plates with diamond filling, each of 120×60 mm in size and 2 mm in thickness. Thermal imaging of samples was carried out. The samples heating range varied from 10 to 90 °С. The test samples were in radiation-convective heat exchange with the environment on both sides. Initially, it was unknown which of the samples has a defect. The thermograms with thermal imaging results were obtained. The analysis of the obtained thermograms was carried out; the temperature distribution on the samples was compared. As a result of this comparison, both the sample with a defect in the form of a crack (a stepwise temperature change in the crack region was observed), and the sample without defect (with the uniform temperature gradient) were determined. Practical relevance. The proposed method of thermal imaging is non-destructive, contactless and allows for the quality control of electronic devices made of highly conductive materials, as well as their thermal properties. The thermal conductivity of the sample can be determined by the temperature gradient and the measured heat flux values. This method is used for research of high-heat ceramic materials (with thermal conductivity above 200 W/(m·K)). Measurements were carried out in steady state behavior. At thermal imaging it is necessary to provide a high radiation coefficient of test sample observed surface. For this purpose, the surface is covered with paint with a radiation coefficient not less than 0.95 or the surface is covered with soot.
Subject of research. This paper focuses on the study of temperature effect on the threshold intensity values for fluorescent mark recording as well as on the features and threshold intensity values for photosensitive material damage during nonlinear phototransformation of chromone derivatives by visible light. Method. Photosensitive chromone derivative compound embedded into polymethyl methacrylate (PMMA) polymer films with 20 μm thickness on the glass substrate were used as samples. Fluorescent marks were recorded by diode pumped passively Q-switched microchip Nd:YAG laser with the second harmonic generation. The wavelength of recording laser pulse was 532 nm, pulse duration was equal to 1 ns. Sample temperature was controlled by Peltier element and was changed in the range of 0–100 °C. Recorded fluorescent marks were registered using confocal laser scanning microscope. Main results. It was shown that cooling of the sample from 25 °C to 0 leads to decreasing of laser induced damage of the sample. Heating of the sample from 25 °C to 100 leads to the decreasing of the threshold intensity for nonlinear recording of fluorescent mark and corresponding efficiency increase of photoinduced transformation process at the fixed energy and duration of laser pulse. Practical relevance. Requirements for thermal stabilization system in the device for nonlinear optical archive information recording can be specified based on acquired results.
The rheological properties research of highly viscous fluid is attractive from both practical and scientific points of view. The research is necessary in the calculation of energy cost of production, equipment, and in the research of their structure of media and flow rules. In general, the rheological properties research of highly viscous fluids, which demonstrate non-Newtonian fluid properties, are carried out on the rotation and capillary viscometers. However, it is rather difficult to use the data obtained in this way in the technical calculations of the equipment. The reason is the difference in hydrodynamic conditions on which the viscosity of non-Newtonian fluids depends. A method for studying the rheological properties of highly viscous fluid is considered based on on the conversion of friction mechanical energy to the heat energy during agitation. The necessity of using the proposed method in rheological studies of highly viscous media has been substantiated. Theoretical explanation of the physical essence of the method is presented and the equation for viscosity calculation is derived. An experimental verification of the suggested method was carried out using the example of determining the viscosity of glycerin aqueous solution at 95 % concentration; the obtained data are compared with known results from the literature. The discrepancy between the experimental and calculated values of the power criterion was no more than 14 %.
The paper presents the study of multi-agent robotic systems in the context of information security providing. The preference is given to decentralized collective strategy of group management due to secure and consensual agent interaction by common communication channel. For the correct and effective functioning of the robotic group there is a necessity in providing security of information transfer via communication channels. We consider the mechanisms of “hard” and “soft” security in robotic systems. Special consideration is given to pragmatic information integrity maintenance. To avoid violation occurrence in this integrity category the method based on credit theory was developed. The method implies regulation of information volume transferred by agents through determination of fixed amount for information conventional units per time unit (installment plan). In case of data retention by an agent its payment value is reduced subsequently, thus, its indebtedness is increased. After installment plan period completion agent’s level of trust and reputation is calculated for each agent. When a new agent is incorporated into the group the credit is determined, at which the new agent will get not full information from the other group members but information reduced by the established interest rate. At the same time, this agent must transmit data in accordance with predetermined installment plan conditions. After credit period completion the decision is made whether the new agent is accepted or blocked. To assess the effectiveness of the proposed method the interaction in robotic group consisted of ten agents was modelled. Two new agents were introduced into the group, and one of them was a saboteur. The threshold value of indebtedness for the agent's acceptance to the group is the half of established credit size. Series of independent tests were carried out and the saboteur was blocked in the 90.8 % of them.
The paper deals with security issues in the environment of "Internet of things" and, in particular, the management of safety access control at MQTT protocol application. We analyzed the most widespread data transfer protocols, CoAP and MQTT, and carried out the analysis of safety methods and means for the MQTT protocol being realized in it or maintained by it. The protocol implements authentication by login and password and allows for cryptographic transformations over the transmitted information via TLS protocol. Third-party services via OAuth protocol and others can be applied for authentication. The authentication takes place by the setting of ACL files or the third-party services and databases. A model is proposed for remote access control management of devices for machine-to-machine interaction under the MQTT protocol based on the Harrison-Ruzzo-Ullman model. The model provides six operators: addition and removal of the subject, addition and removal of the object, addition and deletion of access rights. The proposed model has the form of an access matrix and includes three types of rights: reading, writing and holding. The model is implemented with the result that it is compatible with the version v3.1 of MQTT protocol widely used at the moment. The change of access rights is performed on the basis of the types of messages available in MQTT protocol. An algorithm is considered for service data block creation so that this block can be easily recognized in the message body. The proposed model application gives the possibility to minimize administrator's participation by determination of access rights via the devices themselves without human involvement. Recommendations are given for security policy during information traffic management under MQTT protocol.
The paper presents research in the field of cultural heritage preservation and conservation by means of up-to-date information technologies including semantic approach and sensor networks, in particular. The subject of study is an ontology-based complex automation of museum-specific processes for microclimate parameters control. We present analysis of cultural heritage preservation domain and detect advantages and disadvantages of approaches used nowadays. Existing security vulnerabilities of such class of the systems are presented, threat classification is provided. It is shown that existing security systems and platforms of information systems and knowledge bases, widely used nowadays, cannot not fulfill requirements to security of knowledge bases as a result of many affecting factors and features. The work focuses on both reasons to apply general model-based approach using sensor networks as well as general model-based approach to knowledge security as the only approach able to differentiate facts from inferred knowledge, thus, providing security of the system in general. A set of ontologies is provided for filling the gaps of existing approaches: domain ontology for formalization of museum entities and security ontology for formalization of museum security facilities and for knowledge graph-based inference restrictions depending on access level. Concepts related to network devices and the Internet of things and a new access level are introduced. An innovative Transit Traversal access lever allows for traversing the graph to a final node via other nodes with restricted access. A system based on the provided ontology integrated with Goscatalog enables modernization of climate control and exhibition organization processes as well as ensuring both museum internal security and security of integration with external organizations.
MODELING AND SIMULATION
The subject of this study is the analysis algorithms for studying the behavior of the computer models of electronic circuits with advanced nonlinear elements. The paper gives an experimental comparison of four methods of obtaining two-parametric bifurcation diagrams: histogram of maximal values method, kernel density estimation method, sliding window technique and algorithm based on clusterization of recurrence density plot. The simple memristive circuit with chaotic multi-scroll attractor was chosen as an example for experimental part of the study. The following main results were obtained. Two new algorithms of chaotic system analysis were developed, combining the methods of bifurcation and recurrent analysis with mathematical statistics. New technique for creation of two-parametric high resolution bifurcation diagrams is proposed. This technique is based on sliding average window approach. We also propose the clustering method for plotting precise dynamical maps. The comparative analysis of proposed techniques is described, including the comparison with existing approaches. The study of computational efficiency is performed for integration numerical methods applied for the synthesis of discrete models of the circuit. By comparison of efficiency plots the optimal ordinary differential equation (ODE) solver for computer experiments with discrete models was chosen. The efficiency analysis has shown that the best ODE solver for simple memristive circuit simulation is the semi-implicit extrapolation algorithm of order eight. It is experimentally shown that sliding window average method is the most precise approach for creation of two-parametric bifurcation diagrams. The practical relevance of the obtained results is as follows. New methods of nonlinear systems analysis are applicable for creation of high precision simulation tools for circuits with advanced nonlinear elements. The applications are not limited to the electronic circuits simulation only but also include the possibility to locate hidden attractors in chaotic dynamical systems.
The paper presents preliminary studies and analysis of some properties of alphabets built on the basis of the broadband signal symbols. We study the broadband signal alphabets characters and separate broadband signal symbols. The subject of research includes research methods of synthesis and analysis for broadband radio signals. The synthesis method is formulated for orthogonal alphabets on the basis of signal broadband symbols. The analysis of some statistical characteristics of broadband symbols and messages is performed. It is shown that the distribution of amplitude values of mutually orthogonal signals and messages on their basis has the form of Gauss distribution. The parameter is determined that affects the correlation properties of alphabets of broadband signal symbols. The studies have shown that the characteristics of the correlation function depend on the relative frequency band occupied by the signal broadband symbols. We made estimation and comparison with the theoretical model of the error probability in the channel with additive white Gaussian noise while the use of signal broadband symbols. The simulation results agree with the theoretical expectations and do not exceed the theoretical limit of the error probability. The rate estimation of the information transfer by alphabets built on the basis of orthogonal signal broadband characters is performed. The rate estimation shows significant potential and opportunities of the information seal, especially, with the increase in the relative frequency band occupied by the broadband signal symbols.
The paper presents experimental results on the identification of the inertial parameters and energy dissipation by the symmetric motions of the bodies in a liquid. The object of research is the energy method supplemented by taking into account the coefficients of the dynamic mathematical model of the accelerating and decelerating motion stages and the impact of the solid wall. The subject of research is the problem of exact symmetry of the program motions in various environments and the right choice of the regulator parameters with initial values. The programmed symmetric motions were performed by brushless direct current motor in a small model basin and in the air. When a small tracking error was obtained, the intervals with the highest symmetry were selected. It is necessary to separate the inertial parameters from the dissipative in the calculation formulas. The paper proposed a procedure for iterative tuning of the robust tracking controller, as well as modifications of the adaptation algorithm for the adaptive controller. The right choice of the initial values for the robust controller based on preliminary approximate theoretical calculation improved the quality of the transient responses. Comparative results with the use of the developed method, the least squares method and theoretical formulas are given. The experiments were carried out for the vessel hull and the ellipsoid taking into account the similarity of the Froude and Strouhal numbers in view of the two drafts. The experiment results in the air differ from the results by the nonlinear least squares by no more than 5.1 %. In a liquid with a tracking error about 0.01 % the results differ by no more than 25 %. The theoretical calculation by the known formulas showed different results. The practical relevance of the proposed method is associated with the possibility of high precision parameter identification on a specific program low speed motion with the use of only two angular intervals (with reducing the experiment time).
Subject of research. The research is focused on optimization management tasks of the ground unmanned vehicles in difficult conditions. We showed that it is possible to minimize passage time of road sections with narrowing and maintain security requirements in case of the centralized management. Method. A method of the unmanned cars movement is based on the dynamic programming model. The method provides faster movement than by full search of all possible variants for dangerous road section passage. Such result is achieved by the reorganization of the control task to the class of extreme tasks and the solution of such tasks is based on the Bellman recurrence equation. According to the proposed method a road section is considered as a system with discrete time and finite set of the end positions. Optimal plan of the cars movement is prepared by the central computing device, which has gathered information about road infrastructure and vehicles. The central device is sending control commands to the cars about the change of speed and movement direction in such a way that given criteria and restrictions are satisfied. Main results. The efficiency of the method is demonstrated by the example of driving on a two-lane road. One of the road lanes is blocked for traffic. It is proved that there is a solution that enables all cars to leave the dangerous road section in the shortest time with safety measures. Practical relevance. The proposed method is applicable for control of unmanned vehicles communicating with the central control device by wireless radio. The central control device is a part of the road infrastructure in conditions of isolated environment when there are no any fully autonomous vehicles in the group.
Resonant states (quasi-intrinsic functions) play an important role in the scattering problem and in the description of transportprocesses. We consider the system completeness of resonance states on a finite subgraph for quantum graphs with both finite and infinite edges. The Schrodinger operator acts on the graph edges. The relationship of the scattering problem with the Szőkefalvi-Nagy functional model is taken into account. In particular, the scattering matrix is a characteristic function of the functional model, and the question of the system completeness of resonant states is reduced to factorization type determining of the characteristic function on the Blaschke product and the singular internal function. This fact makes it possible to use an effective sign of a singular factor absence in the decomposition of the characteristic function for the proof of completeness (incompleteness) available in the functional model. The system incompleteness of resonance states for a "ring-type" graph connected to a waveguide at one point (initial graph) is proved. The dependence of the system completeness of resonant states on initial graph geometry changes is studied.
Subject of study. Magnetic resonance imaging (MRI) is one of the most common and popular methods of medical imaging, based on the phenomenon of nuclear magnetic resonance. Despite the absence of ionizing radiation, there are some risk factors for the patient, one of which is the presence of metal structures in the patient's body. The thermal effect arising in the process of magnetic resonance study for patients with ferromagnetic objects is studied. Method. The study of metal objects surface heating was carried out using fiber optic sensors. A phantom was developed with the objects of different materials (steel, ferrite, brass, neodymium magnet) fixed on it. To obtain the maximum possible heating, the corresponding scanning conditions with the highest possible specific absorption coefficient were chosen. Main results. The results of materials heating measuring are presented. It is shown that the temperature of all objects increased in the range of 2.5 to 4.0 °C for total scan time of 90 minutes, while the temperature outside these objects did not change. In this case, heating exceeding the limit of 1 °C for 6 minutes was observed for none of the objects. Practical relevance. The study results can be applied in the development and identification of mathematical models of heat transfer within the framework of comprehensive patient safety in the MRI room. The study opens up the prospect of expanding indications in MRI studies for patients with metallic foreign bodies who need this type of diagnosis (without taking into account other risks: mechanical displacement and deterioration of visualization).
Subject of research. This paper considers a dual-channel algorithm implementation, namely, Minimum Variance Distortionless Response (MVDR), for speech enhancement in the presence of coherence noise using dual-microphone arrays. Methods. The study was performed using analytical models and recordings in an anechoic chamber. Main results. It is shown that the MVDR algorithm can be represented as a combination of a differential algorithm with an adaptive null steering adjustment in the directions of the coherent noise sources and an equalizer that equalizes the spatial-frequency response in the direction of the target source. Practical relevance. The advantage of the MVDR algorithm is automatic null steering in the directions of noise sources. The results are applicable in the design of systems with a large number of microphones.
The up-to-date labor market in the field of IT-technologies in Russia is studied, the required competencies for applicants are analyzed. The problems are shown associated with teaching students to design embedded and cyber-physical systems, as well as the features of traditional approaches to teaching software engineers. We propose an approach to the training quality improvement for software engineers of information systems through the use of low-level programming. The developed modular training laboratory stand SDK-1.1M is presented.